Buch lesen: «Nature's Teachings», Seite 18

These short blades are arranged just like the “studs” on modern shells, and very much resemble them in shape, though not in material.

The Auger finds also a natural representative in the ovipositor of an insect.

That of the common Gad-fly (Œstrus bovis) is most beautifully constructed. It is tubular in form, and is of a telescopic nature, consisting of four tubes of different sizes, the smaller fitting into the larger just as is done with the joints of a common telescope, or those of a Japanese fishing-rod.

The end of the ovipositor is developed into little projections, some of which are armed with hard, sharp points, which act exactly like the cutting edge of the auger. This elaborate appliance is necessary on account of the thick, tough skin of the ox, which the Gad-fly has to penetrate before it can deposit its eggs. Perhaps the reader may be aware of the fact that the modern system of cutting channels in stone with the diamond point, as was so well exemplified in the Mont Cenis Tunnel, is but an imitation, and an imperfect one, of the method adopted by the Gad-fly. We shall soon recur to this instrument.

Striking Tools

If we search the records of antiquity as left by races of men that have for countless ages vanished from the face of the earth, we shall find that in some shape or other the Hammer was a tool in constant use, and that in principle, though not in material, there was no difference between the Hammer of the Stone Age and that of a blacksmith of the present day.

The development of the instrument can easily be traced, especially as it is a tool which does not admit of much elaboration.

The original hammer was evidently a simple stone, and answered equally as a tool and a weapon. As, however, man progressed towards civilisation, he found that the stone itself was insufficient for his needs, and that he required much more force. The most obvious mode of doing so was to take a larger stone, but this expedient soon became valueless, inasmuch as a large stone was a cumbrous instrument to handle, and could not be directed with any certainty or delicacy.

The principle of the lever was then applied to the stone, which was affixed to a handle, and thus became elevated into the rank of a comparatively civilised tool. Sometimes the stone had a hole bored through it, into which the handle of the hammer was inserted, as is the case with most of our present hammers and pickaxes. Sometimes the end of the handle was enlarged, and the stone thrust through it, as is now done with the axes of Southern Africa. Sometimes a long, flexible rod was used by way of handle, the centre of it taking two turns round the stone, and the ends being lashed together. Handles thus made may be seen in any blacksmith’s forge of the present day.

The tool thus made was soon developed into various forms for different uses. By lengthening and pointing the head, it became a pick for loosening the earth. By widening and flattening the head, it became a hatchet; and, by performing the same alteration in the pickaxe blade, it became an adze. I possess a singularly ingenious tool from Borneo, in which the head is movable, so as to be used as a hatchet or adze at pleasure.

In Demmin’s “Weapons of War” many such hammers and axes are figured. One of them is very remarkable. It is an ancient war-hammer made of black stone, and is shaped exactly like a pickaxe, except that one end of the head is carved into a semblance of some animal’s head. The handle is passed through an oval hole in the centre, just like our pickaxes of the present day. This remarkable example of the art of the Stone Age was found in Russia. The head was nearly a foot in length.

Nature possesses many examples of this principle, of which I have chosen two, namely, the Woodpecker and the Nuthatch.

The wonderful power of beak possessed by both these birds is familiar to every one, but it is not so generally known that they do not merely peck after the usual fashion among birds, i.e. delivering the stroke with the force derived from the neck alone. These birds have an additional leverage. Grasping the tree firmly with their feet, they not only peck, but swing their whole bodies with each stroke, bringing their weight to bear upon the object. They thus convert themselves into living hammers, the feet acting the part of the human hand, the body of the bird being analogous to the handle of the hammer, and the head playing the same part in both cases.

In England these birds are not known as well as they ought to be, partly because they are both very shy creatures, and partly because the gradual extinction of forests has deprived them, and especially the Woodpecker, of their undisturbed homes. Yet those who are early risers may see both birds in places where their presence is quite unsuspected, except, perhaps, by those who can recognise the signs which they have left behind them.

There is a common saying to the effect that “a carpenter is known by his chips,” and the proverb is equally true of the Nuthatch and the Woodpecker. Nutshells scientifically split asunder, and jammed into the rough bark of a tree-trunk, betray at once the Nuthatch to the eye of a naturalist; while an accumulation of shattered bark, splinters of wood, and similar debris announces, in equally bold type, that a Woodpecker has been at work.

The power of the Woodpecker’s beak may be gathered from Wilson’s well-known account of an Ivory-billed Woodpecker, which he had wounded and was trying to rear. While staying at an hotel, he locked the bird in his room, and, on returning within an hour, found an astonishing state of things.

“He had mounted along the side of the window, nearly as high as the ceiling, a little below which he had begun to break through. The bed was covered with large pieces of plaster, the lath was exposed for at least fifteen inches square, and a hole large enough to admit the fist opened to the weather boards, so that in less than another hour he would certainly have succeeded in making his way through.

“I now tied a string round his leg, and, fastening it to the table, again left him. I wished to preserve his life, and had gone off in search of suitable food for him. As I re-ascended the stairs, I heard him again at work, and on entering had the mortification to perceive that he had almost ruined the mahogany table to which he was fastened, and on which he had wreaked his whole vengeance.”

The beak of the Woodpecker was employed upon its new master quite as forcibly as upon walls and furniture, but Wilson was of too generous a nature to resent his injuries, and lamented sincerely when the bird died.

The reader will probably observe that the Hammer which has been given as an illustration of this principle is the ordinary geologist’s hammer, and that it has been selected because its head is so formed that one end can be employed for the usual tasks of a hammer, while the other end, with its slight curve and sharp point, is, in fact, a sort of pickaxe, and used for the same purposes. Indeed, this instrument is an almost exact reproduction of the stone hammer which has already-been mentioned, the blunt end being represented by the carved head, and the sharp end by the pickaxe point.

Grasping Tools

Already we have spoken of the Shears and Scissors, together with their mode of action and dependence upon leverage. We now come to a set of tools which, although equally dependent on leverage, develop that power by grasping instead of cutting. Without these tools, the arts and sciences could have scarcely made themselves felt, as there are but few manufactures in which the artificer does not require a grasping power far superior to that of the human hand.

Perhaps the enormous power of the Pincers is never shown to better advantage than in the great iron-works, where enormous masses of white-hot metal have to be brought under the blows of the steam hammer. I do not know of anything which affords a more imposing realisation of the Divine command that man is to subdue the earth as well as to replenish it. There is the vast hammer, striking blows which are felt throughout a large area as if a succession of earthquakes had been let loose. In the furnace there is an enormous mass of iron, heated to such a degree that an unpractised eye could no more dare to look at it than to stare a midsummer sun out of face.

Where are the armies who are to cope with such forces? A few stalwart and grimy men come forward, each man with a curious but unmistakable air of one who wages a war of giants. The furnace door is opened, and out rushes a blinding light which strikes on the eyeballs like a shock of electricity. The men seize the handles of an enormous pair of Pincers, suspended in the middle by a chain, and though no unpractised eye can distinguish the glowing iron from the enveloping fire, they run the Pincers into the furnace, seize the iron, swing it to the anvil, and turn it this way and that way as easily as if it were a feather, while the blows of the gigantic hammer descend upon it, enveloping them in a torrent of sparks which spurt as if they were mere splashes of water, and seem to do them no more harm.

Taking the minor exposition of the Pincers principle and their use, we may mention the ordinary Pincers which are mostly used for drawing nails. Then there are the smaller Pincers called Pliers, all of which are constructed on the same principle, and the chief of which are the Round-nosed Pliers, the Long-nosed Pliers, and the Gas Pliers. Sometimes a mixture of the Hammer and the Pincers is ingeniously contrived, as in the tool which is represented on the right hand of the illustration.

Then we have the still smaller and feebler Pincers of civilised life, such as the Sugar-tongs and the ordinary Coal-tongs of our firesides. Anatomists could have had no practical existence without the Pincers, of which their beautifully constructed and much-elaborated forceps are but variations.

Take, again, the dentist, with his series of shining instruments, which he so carefully keeps out of sight until he has got his patient safely in that awful chair, and which glide, as by a conjurer’s trick, empty into an open mouth, and return in a few seconds with a tooth between their polished jaws.

All these instruments have their parallels in Nature, and in many instances the natural pincers might supply useful hints to modern tool-makers.

In the left-hand upper corner of the illustration is shown the common fresh-water Mussel, which is so plentiful in almost all our rivers and many of our ponds. Its scientific name is Unio margaritiferus. The latter title, which signifies “pearl-bearing,” is given to it because it furnishes the British pearls which were at one time so highly valued.

Like other bivalve molluscs, this Unio has the two halves of the shell fitting quite tightly upon each other, and, when they are drawn together by the contraction of the internal muscles, they can give a very severe pinch. In many uncivilised parts of the world the natives take advantage of this property, and use them as tweezers, chiefly for the purpose of pulling out hairs which they are pleased to think are not needed.

I need not state that with all bivalves the power is increased in proportion to the size of the shell. Even an Oyster can pinch most severely, while the Giant Clam, the shell of which weighs some four hundred pounds, could nearly take off a man’s leg if it seized him.

Mr. J. Keast Lord, in his “Naturalist in British Columbia,” relates an amusing story that was told to him by an old settler respecting the power of the Clam’s grip:—

“You see, sir, as I was a-cruising down these flats about sun-up, the tide jist at the nip, as it is now, I see a whole pile of shoveller-ducks snabbling in the mud, and busy as dogfish in herring time. So I creeps down, and slap I let ’em have it. Six on ’em turned over, and off went the pack, gallows scared, and quacking like mad.”

“Down I runs to pick up the dead uns, when I see an old mallard a-playing up all kinds o’ antics, jumping, backing, flapping, but fast by the head, as if he had his nose in a steel trap; and when I comes up to him, blest if a large Clam hadn’t hold of him, hard and fast, by the beak.”

“The old mallard might ha’ tried his hardest, but may I never bait a martin-trap again if that Clam wouldn’t ha’ held him agin any odds till a tide run in, and then he’d ha’ been a gone shoveller sure as shooting. So I cracked up the Clam with the butt of my old gun, and bagged the mallard.”

Of course the reader will remember that this was only an ordinary Clam, and not one of the giant race.

Below the shell are two very perfect instances of natural Pincers, each acting in a different manner, but on the same principle.

The Earwig is too familiar to need much description, but I may as well state that its pincers are not primarily intended as weapons, although they can be so used on occasion. (I was about to say, at a pinch, but refrain.) They resemble our ordinary pincers in that both blades move equally, and they are so completely under the control of their owner, that the insect uses them with a delicacy of touch that a lady’s fingers could hardly surpass. They are really tools, and not weapons, and are employed for the purpose of folding the wide and delicate wings under the tiny elytra.

There is another insect called the Scorpion-fly (Panorpa), the male of which is furnished with a pair of pincers at the end of a long and flexible tail, articulated just like the tail of a scorpion, and moved in exactly the same manner. It is but a little insect, but its gestures are so menacing as it flourishes its tail about, that non-entomologists may well be pardoned for being afraid of it. Moreover, small as are the pincers, they really can give a smart nip, and make themselves felt on the human skin.

If we want examples of exceedingly powerful pincers, we need only go to the Lobsters and Crabs, especially to the latter, whose claws are often of enormous thickness in proportion to the size of the animal. All those who have visited the seaside know how severe is the pinch of the common Green Crab, comparatively small though it be, and the same may be said of the river crayfish, which is, in fact, a lobster in miniature.

As to the lobster itself, fishermen are so well acquainted with the power of its claws, that they tie them together with string as soon as the animal is caught. Formerly they used to “peg” them, i.e. drive a wooden peg into the joint so as to prevent it from moving. This custom, however, is now prohibited by law on account of its cruelty.

The power of the Crab’s claws is so great that a bite from a large Crab will inflict a severe injury, and render a hand helpless. It has more than once happened that men who have been feeling for Crabs in the recesses of the rocks at low water have been seized, and seriously imperilled, not being able to release themselves from the gripe.

Indeed, it is said that there have been instances where the Crab has held so tightly, that the man has been drowned by the returning tide, no one having come to his assistance. I am, however, inclined to doubt this statement, thinking that the Crab would not be likely to remain in its hiding-place very long after the water came up. Still, that such an idea should be currently believed in many parts of England shows the estimation in which the gripe of the Crab’s claw is held.

CHAPTER IV.
POLISHING TOOLS.—MEASURING TOOLS

Files and Sand-papers.—The Sheffield File and its Structure.—The Equisetum, Mare’s Tail, or Dutch Rush.—Beauty of its Surface when seen through the Microscope.—Sand-paper.—Skin of Dog-fish, Skate, and Shark.—Skate-skin used for Sword-handles.—Distinction between the File and Sand-paper.—Measuring Tools.—The Plumb-rule and the Level.—Their Use in Tunnelling.—The Measure and its Uses.—The Two-foot Rule and the Tape Measure.—Ovipositor of Gall-fly.—Tongues of the Woodpecker, Wryneck, and Creeper.—The Spirit-level and its Uses.—Theodolite and Callipers in Nature and Art.—The Contouring-glass.—Pincers of Earwig again.—Jaws of Insects.—The great Sialis of Columbia.

Files and Sand-papers

HAVING now examined the analogies between the cutting, boring, striking and grasping tools of Nature and Art, we come to those finishing tools which smooth and polish the surface.

The first is the File, an instrument which needs but little description. It consists of a surface of hardened steel, broken up into rough-edged teeth of infinite variety, according to the work which the file has to do. It is rather remarkable, by the way, that at present the English files are infinitely superior to those produced in any other part of the world; that their teeth are all made by hand; and that a genuine Sheffield file will first cut its way through a piece of iron in half the time that would be occupied by a file of any other nation, and then would easily cut its antagonist in two.

As long as the File is intended to work upon metal, there is little difficulty in its manufacture, except that no machinery has yet been invented which can give the peculiar edging of the ridges, and to which is owing the unmistakable “bite” of a real English file.

But there are occasions when the hand of the most cunning file-maker is baffled, and when it is necessary to cut files so delicate that the unaided human eye cannot trace their teeth. Art, therefore, has recourse to Nature, and the cabinet-maker, who cannot obtain any file made by human hands which will answer his purpose in the higher branches of his trade, makes great use of the “Dutch Rush,” as he calls it. It is not a rush at all, but simply a species of Mare’s Tail, or Equisetum, a plant which fills in profusion almost every marshy spot in England.

The peculiar fitness of the Equisetum for this purpose cannot be appreciated even by those who use it until it has been viewed under the microscope. I have now before me a small piece of Equisetum, placed under a half-inch power, and viewed by direct illumination, it being treated as an opaque object.

The microscope reveals at a glance the source of the power which the ingenuity of man has taken advantage of. The surface of the Equisetum is seen to be composed of myriads of tiny parallel ridges, each ridge bristling with rows of flinty spicules, looking very much like the broken glass upon the top of a wall. Minute as they are, these spicules can do their work, and they enable the joiner to finish off work in a manner that could not be accomplished by any tool made by human hands.

I find, by recent inquiries, that modern joiners scarcely, if ever, use the Equisetum, preferring emery-paper as cheaper and more expeditious, and knowing that the popular eye is not able to appreciate the difference of the surface obtained by the Equisetum from that which is given by the finest emery-paper ever made. Wood-carvers, however, if they be of the conscientious kind, and love their work for its own sake, adhere to the Dutch Rush, and are all the happier for it.

Pass we now to the coarser kinds of polishers, the chief of which is popularly known as Sand-paper, and is made by coating some tissue with glue, and scattering upon it sand of different qualities, according to the work to be done. Sometimes, when the work is rough, the sand is large, rough, and coarse, and sometimes, when the work is fine, the sand is so carefully sifted before it is scattered on the glued paper, that there is little distinction between the sand-paper and emery-paper. Linen, by the way, is generally used instead of paper, as being more enduring, less liable to crack, and capable of being folded so as to obtain access to crevices which paper could not touch.

Again in Nature we find a parallel, and the coarse Sand-paper of modern Art has long been anticipated in the scale-clad skins of many fishes.

The accompanying illustration is taken from the skin of a Picked Dog-fish found by myself lying dead on the rocks in Bideford Bay. I cut off a piece for transmission to the draftsman, and found that not only did it feel exactly like cutting through a piece of very common sand-paper, but that it blunted the edge of a new knife in exactly the same manner as would have been done by the roughest of sand-paper.

This kind of skin is common to all the shark tribe (including the Dog-fishes, which are but sharks in miniature), and to the Skate, Saw-fish, &c. I have now before me a small, but perfect example of the Saw-fish, the surface of which is covered with flinty scales like those of the Dog-fish, but very much smaller, requiring the aid of a magnifying lens to distinguish them. Even to guess at the number of them is impossible, for they cover the whole of the body, and extend to the very end of the beak, in some places glittering in a strong light as if pounded glass had been sprinkled all over the fish. One of the most interesting points in their structure is the manner in which they reach the rounded jaws, and there become converted into teeth powerful enough to crush the animals on which the fish live. The structure of these jaws will be explained in a future chapter.

Some of the skates and sharks have these scales of great size, so as to show their formation almost without the aid of a magnifying-glass. This is the case with a species of skate, the skin of which is used by the Japanese for wrapping round the handles of their best swords, and which is greatly valued by that nation, the sword being an almost sacred article in the eyes of a Japanese.

There is a well-known museum in which these swords are labelled as having handles of “granulated ivory.” Now, in the first place, there is no such thing as granulated ivory; and, in the next, a mere glance ought to tell the observer that the so-called ivory is a skin of some sort, worked upon the handle while wet, and kept in its place by copper studs. Even the junction of the edges is perceptible, and yet the authorities of the museum in question, although they have been repeatedly corrected, still persist in calling the skate-skin by the absurd title of granulated ivory.

However, if ivory could be granulated, it would certainly look very much like the skate-skin. When examined closely, the scales, whether of Dog-fish, Skate, Shark, or Saw-fish, are seen to resemble hexagonal cones, not coming quite to a point, but truncated, so as to have an hexagonal flattened tip. They are almost of a flinty hardness, especially at their tips, and on inspection of them the observer is not surprised at the use of Dog-fish skin in place of sand-paper.

Perhaps the reader may ask why the Equisetum should be taken as the prototype of the file, and the skin of the Dog-fish as that of sand-paper. The reason is this. The flinty points of the Equisetum are set upon parallel ridges something like those of a file, while the scales of the Dog-fish are without any apparent order, being crowded against each other like the cutting particles upon the sand-paper. That there should not be an order, and that a definite one, is out of the question. But it has not yet been detected by human eyes, and therefore may be practically treated as non-existent.

Tools of Measurement

In many of the arts, more especially those which belong to engineering and carpentering as a part of architecture, it is absolutely necessary to make sure of a perpendicular line, i.e. a line which, if continued, would reach from any point of the earth’s surface to its exact centre below and its zenith above. Were it not for the power of producing this line, none of the great engineering works of modern or ancient days could have been undertaken.

Take, for example, the wonderful tunnels which have been driven through the earth, of which the Mont Cenis Tunnel is one of the greatest triumphs of modern engineering. Beginning, as the workmen did, at opposite ends of a tunnel many miles in length, and labouring only by the lines laid down by the engineers, the men worked steadily on until they met in the centre.

A few blows, and the then narrow dividing wall was shattered, the men shook hands through the aperture, and then, after enlarging it, leaped wildly from one side to the other, having successfully solved the great problem. With such marvellous precision had the lines been laid, that only a few inches had to be smoothed down on either side, and the sides or walls of the tunnel showed no traces of the junction.

So rapid has been the progress of engineering that a tunnel of a mile in length would, within the memory of man, have been thought as daring a project as was the Mont Cenis Tunnel, which has just been given as an example. Indeed, I know of a railway tunnel, not quite a mile in length, where the engineers had committed some error, so that the two halves, instead of meeting exactly, overlapped each other so much that the mistake was only discovered by the workmen, who heard the strokes of their companions’ picks on their sides, and not in front. Consequently, a great waste of time took place, and the centre of the tunnel had to be made with a double curve, like the letter S, and trains are obliged to slacken speed until they have passed it.

Those who have lived long enough to remember the current literature of the past generation will call to mind the ridicule that was cast upon the idea of a tunnel that should pass under the Thames. That it would be useful if it could be completed, no one ventured to doubt, but that such an idea could be conceived by any one out of a lunatic asylum was rather too much for the journalists of the day. However, the tunnel was made, and so proved the theorists wrong on the one side. And, when made, it was of very little use, which proved them wrong on the other side. Now the proposal to carry a submarine tunnel from England to France excites not half the opposition that was elicited by the comparative child’s-play of a tunnel under the Thames.

The only mode of laying down the lines on which the men worked is by suspending very heavy balls to very fine wires, and then, by means of delicate optical instruments, ascertaining whether the wires are in line with each other.

Familiar instances of the use of this principle may be seen in the plumb-rule and level of the builder or carpenter. The latter, with a base of ten feet in length, is often used by the gardener when he wishes to lay the absolutely level lawns that are required for our modern game of croquet, where the hoops are scarcely wider than the balls, and the lawn has in consequence to be nearly as level as a billiard table.

I may here remark that the name plumb-rule is derived from the Latin word plumbum, or lead, in allusion to the leaden weight at the end of the string. The word “plumber” is due to the same source, and signifies a worker in lead.

These invaluable aids to the development of civilisation are due to one principle, namely, that which we call Gravitation, but which ought more properly to be termed Attraction, and which attracts all parts of the earth towards its centre. We are all familiar with the anecdote of Newton and the falling apple, which may be true or not, but which at all events bears on the present subject. No matter on what portion of the spherical earth a tree may be, every fruit becoming disengaged from it is attracted to the earth, the line which it takes, unless disturbed by external forces (such as wind, &c.), being that which passes from the zenith to the centre of the earth.

This imaginary line is a perfect perpendicular, and the visible line which is formed by the delicate wire of the tunnel-boring engineering instrument, or the comparatively coarse string of the plumb-rule and level, are approximations sufficiently close for practical purposes. So it is in a mathematical proposition. As mathematical lines have no breadth, they are simply indicated or represented by the lines of the figure, the bodily eye being incapable of seeing what is perfectly visible to the mental eye, namely, length without width. So the wire and string perform in practical work exactly the same office which is fulfilled by the lines of a mathematical proposition drawn on paper.

We have already, when treating of the Fall-trap, seen how this principle is brought into operation by those who are utterly incapable of discerning the physical principle, though they can apply it materially with wonderful effect.

It is, perhaps, needless to mention the value of the Measure to any handicraftsman.

I well remember that when, some twenty-four years ago, I was taking lessons from a carpenter in the art of making ladders, gates, fences, hurdles, and other rough-and-ready work, my quaint old tutor related an anecdote of and against himself. He very ingeniously set me to work at boring the auger-holes in the gate-posts which were to be united by the mortise chisel and mallet, and to sweeten the rather severe, because unaccustomed, labour, told me that, when he was a boy, he was doing just the same thing.

Being rather tired of twisting the auger handle (and no wonder either), he withdrew the instrument, and put his finger into the hole by way of ascertaining its depth. Immediately he found himself on his back, having received a tremendous box on the ear from his father, whose parental wrath was excited by the idea of his son condescending to use his finger by way of measure, when he had a two-foot rule in its own special pocket.

There are, however, many cases where even a two-foot rule would be insufficient for the work, and where a measure of thirty or forty feet is needed.

Now, there is no doubt that by means of a two-foot, or even a six-inch, rule any number of feet might be measured accurately; but, considering the number of junctions that have to be made, it is not likely that any pretence to accuracy could be insured.

Then, a rod of forty, or even of twenty, feet in length would be awkward and unmanageable, and the only plan left is to take a string or cord of the requisite length.